Some vehicle brake systems use both regenerative and frictional braking to meet driver braking demand, and do so by partitioning the overall driver braking demand into a regenerative component and a frictional component. In order to guard against potential failures in the regenerative braking system, some vehicle brake systems place a limit or threshold on the regenerative component so that it does not exceed a level where the frictional braking system can, if needed, quickly intercede in the event that a regenerative braking failure were to occur. While this approach may address some of the concerns regarding potential regenerative braking failure, it can also limit the role of the regenerative braking system and thus reduce the overall fuel efficiency of the vehicle.